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Technology and characterisation of GaAsN/GaAs heterostructures for photodetector applications

Beata Ściana 1Damian Radziewicz 1Damian Pucicki 1M. Tlaczala 1Jarosław Serafińczuk 1Iwona Zborowska-Lindert 1Przemysław Poloczek 2Grzegorz Sęk 2

1. Wrocław University of Technology, Faculty of Microsystem Electronics and Photonics (WEMIF), Janiszewskiego 11/17, Wrocław 50-372, Poland
2. Wroclaw University of Technology, Institute of Physics, Wybrzeże Wyspiańskiego 27, Wrocław 50-370, Poland


The nitrogen – containing conventional AIIIBV semiconductor alloys, so called diluted nitrides (AIIIBV-N), have been extensively studied recently. Unusual properties of these materials such as a large band gap bowing coefficient b (40 eV for GaAs1-xNx with x < 0.1%) and a large conduction band CB offset (> 300 meV) come mainly from a large size difference between N (0.068 nm) and As (0.121 nm) and a large electronegativity of N (3.04) compared to Ga (1.81) and As (2.18). These features make AIIIBV-N alloys very promising for applications in lasers and very efficient multijunction solar cells. There are not much papers devoted to applying these materials in photodetector device structures.

This work presents the technology and properties of undoped GaAs1-xNx/ GaAs heterostructures used as active regions in the construction of MSM and PIN photodetectors. The atmospheric pressure metal organic vapour phase epitaxy (AP-MOVPE) was applied for growing MSM test structures with the nitrogen contents varied form 0.5 % to 1.74 %. The thickness of the absorption GaAs1-xNx layer was changed from 98 nm to 135 nm. The structural and optical properties of these structures were examined using high resolution X-Ray diffraction HRXRD, photoluminescence PL (T = 80¸ 250K) and photoreflectance spectroscopy PR (T = 300 K). The DQW (double quantum well) PIN test structure was grown by radio-frequency molecular beam epitaxy RF MBE. The undoped active region consisted of two 10.5 nm thick GaAs0.99N0.01 wells separated by 15.2 nm thick GaAs barrier layer was surrounded by undoped 200 nm thick GaAs and 100 nm thick p+-type GaAs from the top of the structure and by undoped 200 nm thick GaAs and 500 nm thick n+-type GaAs from the n-type GaAs substrate. The properties of the DQW active region were examined using PL measurements (T = 300 K). Chemical wet etching was used for active region delineated to obtain the 80 μm × 60 μm MSM and Ø 125 μm PIN islands. The Ti/Pt/Au and Cu/Au metallization was applied for multifinger Schottky MSM contacts with 1 μm/ 2 μm and 1.5 μm/ 3.5 μm finger width/ finger spacing. In the case of PIN device planar structure the Pt/Ti/Pt/Au and AuGe/Ni/Au metallization was used for the top ring contact to p+-GaAs and for the bottom contact to n+-GaAs, respectively. Dark and illuminated by different wavelength lasers (λ = 650, 780, 850, 904, 980 nm; excitation power 20 and 40 μW) DC current-voltage characteristics were measured under the bias changed from –5 V to 5 V. Based on the obtained results the main device parameters as a dark current and a spectral response were estimated for both MSM and PIN structures.


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Related papers

Presentation: Poster at Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth, by Beata Ściana
See On-line Journal of Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth

Submitted: 2007-01-15 14:11
Revised:   2009-06-07 00:44